`The ideal vehicle for extensive aquatic monitoring is mobile underwater sensor network (M-UWSN). M-UWSN is significantly different from terrestrial sensor networks: (1) radio channels do not work well under water. They must be replaced by acoustic channels, which feature long propagation delays, low communication bandwidth and a high channel error rate; (2) while most ground sensors are static, underwater sensor nodes may move with water, as introduces passive mobility. Due to the complex environment properties and the unique characteristics of acoustic channels, M-UWSN demands new research at every level of the protocol suite. In this project, we investigate three key networking problems for M-UWSN: multiple access, multi-hop routing and reliable data transfer. For multiple access, we study a reservation-based approach for dense networks and an adaptive protocol for unevenly-distributed networks. For multi-hop routing, we design a scalable geo-routing protocol and improve its robustness by effectively handling routing "holes". For reliable data transfer, we explore both FEC (Forward-Error-Correction) coding and network coding approaches, aiming to enhance network robustness while reduce communication cost. The accomplishment of this research will enable and/or enhance a wide range of aquatic applications in scientific research and national security/defense. The results will include (1) a set of protocols and algorithms for the three networking problems; (2) integrated solutions and user guidelines for different aquatic applications; (3) a simulation platform and real testbeds. The research results will be incorporated into both undergraduate and graduate courses. Both the simulation platform and real testbeds will be accessible to the community.
In recent years, there has been an increased interest in monitoring aquatic environments for scientific exploration, commercial exploitation and coastline protection. The ideal vehicle for extensive aquatic monitoring and exploration is underwater sensor network (UWSN). UWSN is significantly different from terrestrial sensor networks: (1) radio channels do not work well under water. They usually have to be replaced by acoustic channels, which feature long propagation delays, low communication bandwidth and high channel error rates; (2) while most ground sensors are static, underwater sensor nodes may move with water or be self-propelled, as introduces passive mobility or proactive mobility. Due to the complex environment properties and the unique characteristics of acoustic channels, UWSN demands new research at every level of the protocol suite. This CAREER project has explored three key networking problems for UWSN: medium access control (MAC), multi-hop routing and reliable data transfer. For MAC, we have studied a reservation-based approach for dense networks and an adaptive protocol for unevenly-distributed networks. For multi-hop routing, we have designed a scalable geo-routing protocol and improved its robustness by effectively handling routing "holes". For reliable data transfer, we have explored both FEC (Forward-Error-Correction) coding and network coding approaches, aiming to enhance network robustness while reduce communication cost. The research efforts have focused on the development of Aqua-Sim (an underwater network simulator), and the design and evaluation of the proposed MAC protocols, routing protocols, and reliable data transfer protocols. In addition, a prototype lab testbed called Aqua-Lab, an open network architecture called Aqua-Net, and a lake testbed called Aqua-TUNE have been developed for tesing various stages of the proposed underwater sensor network research. Extensive filed testings have been conducted in lakes, bays, and open seas. Based on experiences from various field experiments, the research efforts have further focused on identifying the real system features and studying their impacts on various protocols in medium access control, routing and reliable data transfer for underwater sensor networks. Theoretically, the developed protocols and algorithms for the three networking problems in UWSN have made significant contributions in advancing the field of underwater communications and networking (many of the resulted publications have received high citations based on Google Scholar); system wise, the resulted simulator, Aqua-Sim, has been widely used by the community; in the real world, various field testbeds have facilitated extensive testings of networking protocols, providing useful guidelines toward integrated solution design for real aquatic applications. In terms of broader impacts, the research results from this CAREER project have been well incorporated into both undergraduate and graduate courses. Further, many undergraduate and graduate students have been proactively involved during the whole course of the project and five Ph.D. graduates have been partially supported by this grant. Higher performance networking solutions will greatly facilitate the development of various underwater networks and access to open platforms will enable a wide variety of researchers to pursue their research and development efforts in underwater networking and applications.
